WHAT IS MEAN SEA LEVEL PRESSURE?
Mean sea level pressure (MSLP or SLP) is the pressure at sea level or (when measured at a given height on land) the station pressure reduced to sea level by an appropriate altitude dependant formula. Ships at sea and low-lying weather stations must add (rather than subtract) a small correction to their barometric pressure readings (called “station pressure”) to obtain the SLP. This is the pressure normally given in weather reports on radio, television, and newspapers. When barometers in the home are set to match the local weather reports, they measure pressure reduced to sea level, not the actual local atmospheric pressure. The reduction to sea level means that the normal range of fluctuations in pressure is the same for everyone. The pressures which are considered high pressure or low pressure do not depend on geographical location. The altimeter setting in aviation, with two meanings either QNH or QFE (maybe one of these is MSLP above), is another atmospheric pressure reduced to sea
